<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        /* .three > input:focus {
            color: blue;
        } */

        /* div>a {
            color: red;
        }
         */

        .light
        {
            background-color:antiquewhite;
            color: black;
            width: 100%;
            height: 100%;

            /* border: 2px dotted red; */
        }

        .dark
        {
            background-color: black;
            color: aliceblue;
            width: 100%;
            height: 100%;
        }
        
        /* div {
            background-color:aquamarine;
            border: 11px solid black;
            width: 100px;
            height: 100px;
            box-sizing: border-box;
        } */

        
        
    </style>
</head>
<body>
    <div class="light" id="ColorMode" onclick="ChangeColor()">
        hello<br>
        hello<br>
        hello<br>
        hello<br>
    </div>


    <!-- <div class="three">
        <input type="text">
        <input type="text">
        <input type="text">
    </div> -->

    <!-- <div>
        <a href="#"> xxx
            <ul>
                <li><a href="">yyy</a></li>
                <li><a href="">zzz</a></li>
            </ul>
        </a>
    </div> -->
</body>

<script>
    function ChangeColor()
    {
        let colMode = document.querySelector("#ColorMode");
        if(colMode.className == "light")
            colMode.className = "dark";
        else
            colMode.className = "light";
    }
</script>

</html>